The present invention relates generally to the storage and retrieval of images and more particularly, to a reflective diffraction grating having stored color images that are retrievable using light, and to a method of producing the grating.
Photographic film has been used to store color images for many years. Image resolution for film is limited by the size of the individual grains in the unexposed film, which for the case of three-layer registry of color microfilm is about 10 microns. In addition, film undergoes continuous chemical degradation, which adds to the difficulty in preparing and preserving high-resolution color images.
Other types of media, more durable than film, have also been used to store images. Durable data storage media have, for example, been described in U.S. Pat. No. 5,721,687 to Bruce C. Lamartine et al entitled xe2x80x9cUltrahigh Vacuum Focused Ion Beam Micromill and Articles Therefromxe2x80x9d, and in U.S. Pat. No. 5,773,116 to Bruce C. Lamartine et al entitled xe2x80x9cFocused Ion Beam Micromilling and Articles Therefromxe2x80x9d, both incorporated by reference herein. The durable data storage media are produced by exposing a target substrate to an ion beam under vacuum. The ion beam mills away portions of the substrate surface to form pits. The presence or absence of a pit can be representative of binary characters, i.e. ones or zeros. An aggregate of pits can also be used to form characters that produce images. Greyscale images, for example, may be produced from original black and white images or color images. If the original image was a color image, the color can be recovered from the greyscale image by colorizing, a mathematical reconstruction process that involves using an algorithm to relate the depths of the individual milled pits to color densities of three colors: red, green, and blue. The algorithm assigns a unique color value in a bitmap derived from a table containing the numerical greyscale values used to form the greyscale image.
While colorizing enables the recovery of a color image from a greyscale image stored in durable medium, it is an indirect and complex method. A more direct and less complex method of retrieving color images stored in a durable medium would simplify the retrieval of the stored color images.
Therefore, an object of the present invention is a method of storing color images on a durable storage medium that can be retrieved easily.
Another object of the invention is to provide a durable storage medium having at least one, easily retrievable stored color image.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes a method for storing color images in a durable medium. The method involves placing a crystalline or highly polished durable medium having a substantially flat target surface within a vacuum environment; producing a computer data file adapted to operate a computer-controlled, focused ion beam to mill blazed pits into the durable medium; and exposing the durable medium to the computer-controlled ion beam in a vacuum environment, the computer controlled focused ion beam controlled by software utilizing the data file to mill blazed pits into the durable medium, whereby the durable medium is transformed into a durable storage medium with at least one stored color image. When the milled surface of the durable storage medium is exposed to polychromatic light, the stored images can be retrieved.